When Sana Raoof was called to the stage to receive the Intel Foundation's top honour at the Intel International Science and Engineering Fair in Atlanta last week, someone in the crowd yelled that the announcement was supposed to be just a joke.

Sana fell for that, albeit momentarily.

Seconds later, when dozens of videographers and still cameramen started focusing on her and the giant television screen on the side of the stage showed her cherubic face, the 17-year-old high school senior realised that she was in fact one of the top three winners of Intel Foundation's Young Scientist Award.

"I just could not believe it. My knees were shaking when I had to get up and walk towards the stage. I am lucky that I did not pass out or something," Sana said, recalling the May 16 award ceremony, in which Intel selected three top young scientists at the end of the world's largest pre-college science fair, held between May 11 and May 16. Each of them got $50,000 in college scholarships from the Foundation.

Besides Sana, who lives with her physician parents in Muttontown, New York, two others � Natalie Saranga Omattage, of Cleveland Mississippi and Yi-Han Su of Chinese Taipei � were selected from among more than 1,550 young scientists from 51 countries, regions and territories for their commitment to innovation and science.

"To see young students from around the world develop innovative solutions to problems confronting society shows the true power of this international science fair," said Intel Corporation Chairman Dr Craig Barrett. "Sana, Natalie and Yi-Han demonstrate that dedication to science inquiry can transcend boundaries and show what we can accomplish when we focus on education and science."

Sana's research provided new insight into how a better understanding of mathematical Knot theory could help resolve classic biochemical problems. Her work focused specifically on the Alexander-Conway polynomial invariant for chord diagrams, to help prove how to classify molecules on a structural basis.

The Knot theory is the mathematical study of knots. A mathematical knot has no loose or dangling ends, as the ends are joined to form a single twisted loop. The main problem of Knot theory is distinguishing between various knots and classifying them.

Sana solved the problem first at the Massachusetts Institute of Technology, where she went last summer as a high school junior to attend a programme on math, during which she got a chance to interact with Nobel Laureates and celebrated professors at least thrice a week.

Sana, who already knew a lot about the Knot theory, got a great introduction to the theory and research papers on the subject. She said she noticed that a lot of authors had complained that there is no way to guarantee that two different knots are the same."That is how I got the idea, and I spent the rest of the summer trying to prove that we can guarantee whether two knots are the same, or different. My mentor confirmed that my proof was accurate at the end," she recalled.

At the Intel science fair last week, she fine-tuned the same research. Sana said her research led her to realize it has a lot of applications in biochemistry, because DNA and proteins can be modeled as knots. She figured out that if she can tell mathematical knots apart, it means that she can tell molecules apart based on their structure. It may have practical application in criminal investigation such as easily identifying a criminal's DNA.

"When I looked into this more, I realised that the more knotted the DNA is, the faster it can move, and my mathematical proof offers the way to quantify knots," she said.

Where does a 17-year-old get the confidence to do what she did? "I think in order for girls to survive in math these days they need to be extremely confident, because there is a lot of sexism out there and everybody can feel it. For example, in the Intel fair, only 12 percent of the projects in Mathematics were done by girls. So, it is very obvious that you need to be very self-confident," she said. Interestingly, all three top prizes went to women, all aged 17.

Sana, whose mother Sabiha Raoof and father Sohail Raoof are doctors, attributes a lot of her success to her family members, particularly grandfather Dr Abdul Raoof, a retired United Nations official who inspired her to do better in math and science. "My grandfather has always pushed me ahead and made me very competitive. He has been teaching me everything since I was like two or three years old," she said.

"I guess I am very lucky that I have been raised in sort of a feministic environment. Otherwise, if I had no confidence, probably I would not have done this project at all," she said.

Sana's mother hails from Kashmir and her father is from Delhi; she was born and raised in the United States, and lives in the family home along with her grandparents. True to the teachings of her grandfather, who pushed her to excel at anything she turned her hand to, Sana has a great track record not just in math or science, but also in debate and running track. Last month, she won the New York State Forensic League tournament championship for the second consecutive year.

She believes she is very lucky to have parents who take time out to travel with her, so she can participate in tournaments. "My dad is actually a very good speaker, so I debate him sometimes," she said. Her interests seemingly run in the genes: her father, a 'great runner', placed seventh at the US national championships in the half mile, and will run track next year at the Harvard University.

Sana plans on getting an MD in an area like critical care medicine, and a PhD in mathematical biology; to this end, she will enter Harvard this fall, with math major and pre-med as minor.

"I definitely want to do both. My parents always wanted me to be a doctor, even though they said I could do whatever I wanted. My parents were at first worried that maybe I was taking on a lot of things, but they got used to it and want me to do whatever I want to do," she said.

Did she have to put on her feminist armour and battle her dad for this freedom? "I guess in my family, everyone has to be a little bit feministic to be used to me," she said.

She loves philosophy, and teaches the subject in junior classes at her school. "I found that it really helps me with my debating skills, because a lot of debates have ethical issues anyway, and also it is really nice because track, debate and research are all individual competitive things, but teaching a philosophy class is a way for me to learn non-competitively, feel fulfilled and really help younger kids," she said. Like in mathematics, she has acquired knowledge in philosophy through independent reading.

"A lot of the things that I do in high school are done independently, because if you kind of want to shine in life, you have to really help yourself. So, I have done a lot of reading on my own," she said.

By her own admission, whenever she has free time, she either reads about Knot theory or about philosophy, mostly on the Internet.

None of this makes her an atypical teen -- she loves music and the movies, but hardly finds time for all that, given her varied interests. "I have seen Harry Potter [Images], and I recently watched Om Shanti Om. It was good. Had a lot of music, I guess," she said.

For all her hard-headed practicality, Sana is a dreamer; her constant dream is to do something that hasn't been done before, especially something people believe women cannot do. "I have always dreamed of curing some disease that nobody has been able to cure, something that kills a lot of people, and if I ever get to do something on that, it would be awesome," she said.

Though she talks, at the drop of a cue, about the need for women to be independent, there is a child-like, almost na�ve side to her that surfaces in conversation. "I would try and make it [the cure] available for everybody," she said, clearly not taking much notice of the pharmaceutical lobby.

"I do not want to get rich out of it. I would kind of like to donate everything. My parents think I am kind of crazy, but I would like to live in a small house and whenever I get something I would like to give it to people who are sick, or give it for promoting education of women in countries where only boys are educated."

Her other dream is to be able to continue to run and compete in races till she is really old. "I want to be one of the 95-year-old women that would keep everyone at the end of the track because she is still running, although everyone else on the track has done with the race. I want to keep on running as long as I can."